Machine countersunk the left & right subpanels for attachment of nutplates and the F803C attach flange. Next, I edge finished both of the subpanels on the scotchbrite wheel. Got out the Van’s plastic fresh air vent to see how it would fit on the left subpanel. Hmm, not real impressed with the plastic vent--looks like I will be ordering the aluminum vents. This may temporarily delay progress on the panel. Really prefer to cut the holes for the vents before riveting the subpanels to the attach flange.